Control device for heating sources of cooking appratus

Abstract

Control device for the heating sources of a cooking apparatus, in particular of a cooking surface, possessing a set of neighboring heating sources and a smooth sheet of vitroceramic glass, of uniform thickness, inparticular covering the entire surface, having a plurality of sensitive keys actuated by the approach of a user's finger into contact or into immediate proximity with the surface of the sheet. According to the invention, each key is associated with a specific source and is formed by the two metal armatures, disposed substantially in the same plane, of a single capacitor carried by a printed circuit board attached under the sheet opposite the upper surface thereof, the capacitor having its first armature connected to a pulse generator and its second armature connected to a differential comparator, the first, peripheral armature having a general U-shaped profile which surrounds the second, central armature in a manner such that the approach of the finger directly over the capacitor but on the other side of the sheet, towards or against its upper surface, modifies its capacitance and causes a change of state at the output of the differential comparator capable of varying the electrical voltage supplied to the source associated with the key.

I claim: 
     
       1. Control device for heating sources of cooking apparatus having a cooking surface, comprising a continuous smooth sheet of vitroceramic glass of generally uniform thickness and having upper and lower major plane surfaces,   a set of neighbouring radiant heating sources mounted next to said lower surface of said glass,   a plurality of sensitive keys disposed adjacent to the lower surface of the glass being actuated by an approach of a user's finger into contact or into immediate proximity with the upper surface of the sheet opposite each key,   each of the plurality of the keys being connectively associated with a specific one of the set of sources and said each of the plurality of keys consisting of a first and a second of two metal armatures being disposed substantially in the same plane,   the two metal armatures generally comprising a single capacitor carried by and formed as part of a printed circuit board attached to the lower surface of the sheet,   the capacitor having the first of the two armatures connected to a pulse generator and the second of the two armatures connected to a differential comparator having an output, and   the first of the two armatures having profile means which encompasses and surrounds the second of the two armatures in a manner such that the approach of the finger directly over the capacitor but on another side of the sheet, towards or against its upper surface, modifies a value of the capacitance and causes a change of state at the output of the differential comparator to effect varying of electrical power supplied to one of the set of sources, and   said printed circuit board carrying the capacitor, the pulse generator and the differential comparator is embedded in a layer providing insulation and protection against moisture, and is adjacent the lower sheet of vitroceramic glass and in close contact therewith.   
     
     
       2. A control device according to claim 1, wherein a thin intermediate layer of resin is disposed between the glass forming the sheet and the printed circuit board. 
     
     
       3. A control device according to claim 2, wherein said insulating layer is constituted by a silicone resin, and the thin intermediate layer being formed by means of an epoxy resin. 
     
     
       4. A control device according to claim 1, wherein the sensitive keys are associated two by two, in pairs, with each heating source, to bring about respectively, in each pair, an increase and a decrease in the supply power delivered to the set of sources, in order to regulate a desired rate of heating. 
     
     
       5. A control device according to claim 1, further comprising on said printed circuit board control keys together with a key for locking the latter in an instaneous state, in order to keep a chosen rate of heating. 
     
     
       6. A control device according to claim 1, further comprising display means for providing indication of heating rates constituted by light-emitting diodes mounted in the vicinity of each of the keys beneath the glass of the sheet, and   the diodes disposed in line are lit or extinguished one at a time in accordance with the increase or decrease in the current of the source associated with the each pair of keys.   
     
     
       7. A control device according to claim 1, wherein said sensitive keys are controlled by a microprocessor via interface circuit means which receives all the signals outputed by the differential comparators associated with the keys. 
     
     
       8. A control device according to claim 1, further comprising monitoring means including means capable of cutting the current to the sources responsive to and in the event of overflowing of liquids on top of the glass sheet or of the action extending beyond a specific length of time, of overheating of the keys circuits, or of positioning of hot metal receptacles too close thereto.